Radiation Effects in SiGe Devices

1
Radiation Effects in SiGe Devices Bongim
Jun, Gnana Prakash, Akil Sutton,
Marco Bellini, Ram Krithivasan, and John D.
Cressler MURI Review Vanderbilt
University, Nashville, TN June 13, 2006
School of Electrical and Computer Engineering 777
Atlantic Drive, N.W., Georgia Institute of
Technology Atlanta, GA 30332-0250
USA cressler_at_ece.gatech.edu Tel [phone] /
http//users.ece.gatech.edu/cressler/
2
The SiGe Success Story

• Rapid Generational Evolution (full SiGe BiCMOS)
• Making Significant In-roads in High-speed
  Communications ICs
• Many DoD-Relevant Opportunities

- very high performance SiGe HBT best-of-breed
Si CMOS - RF to mm-wave analog digital
passives for integrated SoC / SiP
4th
3rd
2nd
1st
3
Half-TeraHertz SiGe HBT!

• 510 GHz peak fT at 4.5K!
• Worlds First Half-TeraHertz Si-based Transistor
• Lots of Steam Left for SiGe HBT Scaling

To appear in IEEE Electron Device Letters, July
2006
4
Applications
Defense Navigation Automotive Communicati
ons
5
SiGe mm-wave SoC

• Wireless 60 GHz (ISM band) Data Links (1.0
  Gb/sec!)

DARPA Funded
                 
Courtesy of Ullrich Pfeiffer of IBM
6
SiGe Radar Systems
Single Chip X-band SiGe T/R (4x4 mm2)
MDA Funded
Begs For SiGe!
Potential Paradigm Shifting Impact for Phased
Array Radar!
7
Extreme Environments

• Cryogenic Temperatures (e.g., 77K -196C)
• High Temperatures (e.g., 200C)
• Radiation (e.g., Earth orbit)

Cars
Drilling
Moon / Mars
CEV
Aerospace
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Total-Dose Response
Multi-Mrad Total Dose Hardness (with no
intentional hardening!) Radiation Hardness Due
to Epitaxial Base Structure (not Ge) - thin
emitter-base spacer heavily doped extrinsic
base very thin base
                 
4th
3rd
200 GHz SiGe HBT
2nd
1st
63 MeV protons _at_ 5x1013 p/cm2 6.7 Mrad TID!
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Single Event Effects

• Observed SEU Sensitivity in SiGe HBT Shift
  Registers
• - low LET threshold high saturated
  cross-section (bad news!)

50 GHz SiGe HBTs
Goal
The Achilles Heel of SiGe and Space!
1.6 Gb/sec
P. Marshall et al., IEEE TNS, 47, p. 2669, 2000
10
The Intuitive Picture

• Collector-substrate (n/p-) Junction Is a Problem
  (SOI solves this)
• Lightly Doped Substrate Definitely Doesnt Help!

Heavy Ion (GeV cosmic ray)
Very Efficient Charge Collection!
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3-D TCAD Modeling
Collaboration with R. Reed of Vanderbilt
Univ. and G. Niu of Auburn Univ.
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TCAD Charge Dynamics

• Most Charge Collection Occurs Through C/Sx
  Junction
• Long Collection Times for High LET Ion Strikes
  (nsec!)
• Deep Collection Depth (16µm!)

Drift Diffusion
Collaboration with R. Reed of Vanderbilt and
Guofu Niu of Auburn Univ.
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TCAD to Circuits
5HP
8HP
Standard Master Slave
OUT
DATA
CLOCK
UPSETS
Hit
RamHard RHBD
OUT
DATA
CLOCK

• 3D Simulation I(t), Deep Strike, LET10, Vsx
  -4V (4 GB/s)

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SEU Tolerant Latches

• Reduce Tx-Tx Feedback Coupling Internal to the
  Latch
• Circuit Architecture Changes Transistor Layout
  Changes

Dual-Interleaved
Limiting Cross-section (no errors!) First
Successful Hardening of SiGe!
Leverage DARPA RHBD Program DTRA /
NEPP
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Outline

• Some Reminders
• New Total Dose Effects in Bulk SiGe HBTs
• New Cryogenic Irradiation Results
• New Results on SiGe HBTs on Thin-Film SOI
• A First Look at SiGe MODFETs
• Progress / Plans

16
Source / Rate Effects

• EB spacer ? SiO2/Si3N4 composite stack
• Variation in ?JB damage with dose rate for
  different sources not large
• Dose enhancement effects apparently observed for
  x-ray damage
• photon interaction with Cu/W metallization ?
  enhanced x-ray damage?
• results qualitatively agree with Geant-4 MRED
  simulations on SRAMs

x-ray dose enhancement
Cu/W studs above EB spacer
Collaboration with MURI Vanderbilt Team Leverage
DTRA / NEPP
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Source / Rate Effects

• STI oxide ? thermal CVD (different interface to
  EB spacer)
• Increase in inverse mode ?JB with dose rate (60Co
  and x-ray)
• electron-hole pairs escape recombination ?
  increased charge yield
• secondary electrons generated with low stopping
  power ? increased damage

E B C
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Reliability Issues

• Preliminary study of possible reliability stress
  path dependence
• Mixed-mode stress (high VCB high JE) prior to
  proton irradiation
• 63 MeV protons / 3000 sec mixed-mode stress
  (JE40mA/µm2, VCB3V)
• No change observed in post-radiation response
  after 3000 s of stress

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Reliability Issues

• 1Mrad(SiO2) prior to 3000 sec mixed-mode stress
• Forward and inverse mode ?JB independent of
  pre-stress condition
• More work needed
• increase stress time beyond 3000 sec vary
  current density during stress
• explore reverse EB stress response

20
Outline

• Some Reminders
• New Total Dose Effects in Bulk SiGe HBTs
• New Cryogenic Irradiation Results
• New Results on SiGe HBTs on Thin-Film SOI
• A First Look at SiGe MODFETs
• Progress / Plans

21
The Moon
(Classic Extreme Environment!)
Rover / Robotics

• Temperature
• 120C to -180C
• 28 day cycles
• -230C in shadowed polar craters
• Radiation
• 10s of krad (modest)
• single event upset (SEU)
• solar events
• Many Different Circuits
• digital / analog library
• ADC / DAC
• RF
• power
• control functions
• sensor interfaces

Get Rid of the Centralized Warm Box
Large GT-led NASA Funded Effort (RHESE) Targeting
RLEP-2
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Cryo-T Irradiation

• Less Degradation For Devices Irradiated at 77K
  Compared to at 300K
• Damage is Produced Even in the Absence of
  Significant Thermal Energy

Leverage DTRA / NEPP
63 MeV protons
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Cryo-T Irradiation

• 300K Irradiation 77K Measurement vs. 77K
  Irradiation 300K Meas.
• 300K Irradiation Appears to Produce More Damage
  Than 77K Irradiation

• Interesting Physics AND Bodes Well Lunar Apps
  of SiGe

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Cryo-T Irradiation

• Answer Appears to Depend on the Technology Node!
  
• In 200 GHz 8HP Devices, Forward-Mode ?IB is
  Larger for 77K Irradiation
• We Will Focus Some More Attention Here

25
Outline

• Some Reminders
• New Total Dose Effects in Bulk SiGe HBTs
• New Cryogenic Irradiation Results
• New Results on SiGe HBTs on Thin-Film SOI
• A First Look at SiGe MODFETs
• Progress / Plans

26
Intuitive Picture for SEU

• Collector-substrate (n/p-) Junction Is a Problem
• Low Resistivity Substrate (8-10 ohm-cm)
  Definitely Hurts!

SOI
J. Pellish et al., NSREC 06
Leverage DTRA / NEPP NAVSEA
Very efficient charge collection (to 16 um!) An
obvious solution move to SOI!
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Device Technology

• IBM Research Collaboration (J. Cai)
• TSi 120 nm / TBOX 140 nm (compatible with
  130 nm SOI CMOS)
• Substrate Can Be Used as an Active 4th Terminal
• True 2-D Device (fundamentally different from
  conventional SiGe HBT)

                 
 
VSUB
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X-ray Irradiation

• IB Leakage Increases at Low VBE (EB spacer
  damage)
• IB Decreases at High VBE (RC effect)

Collaboration with MURI Vanderbilt Team
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X-ray Irradiation

• Partially Depleted Devices Irradiated for the
  First Time
• Larger Excess Current with Respect to 63 MeV
  Protons

Fully Depleted Partially Depleted



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Outline

• Some Reminders
• New Total Dose Effects in Bulk SiGe HBTs
• New Cryogenic Irradiation Results
• New Results on SiGe HBTs on Thin-Film SOI
• A First Look at SiGe MODFETs
• Progress / Plans

31
SiGe MODFETs

Collaboration with S. Koester at IBM
32
SiGe n-MODFETs

Collaboration with S. Koester at IBM
33
nMODFET Irradiation

• Peak gm and peak fT decrease with Radiation
• Impact of Displacement Damage on Transport?

Leverage DTRA / NEPP
63 MeV protons
34
Georgia Tech Focus

• Many Fundamental Issues in SiGe Need Attention
• - improve our understanding of basic damage
  mechanisms (TID SEU)
• - understand observed dose enhancement / source
  dependent effects
• - understand the effects of operating
  temperature on damage mechanisms
• - explore other SiGe HBT variants (e.g., SiGe
  HBT on SOI, C-SiGe)
• - explore other (new) SiGe-based devices (e.g.,
  SiGe MODFETs)
• - improve 3D modeling and understanding for SEU
  (with R. Reed)
• - explore metalization / overlayer effects
  (GEANT4 with R. Reed)
• - explore device-to-circuit coupling (mixed-mode
  TCAD with R. Reed)

• Leverage of Significant SiGe Hardware / Testing
  Activity
• - many SiGe tapeouts at Georgia Tech (IBM, Jazz,
  etc.) devices circuits
• - DTRA / NASA-GSFC (NEPP)
• - DARPA RHBD Program
• - NASA SiGe ETDP RHESE Program (Lunar apps)

35
Progress / Plans
Dose Enhancement Effects / Source Dependence in
SiGe HBTs - push deeper into the mechanisms
more data TCAD GEANT4, etc.
Explore the Role of Temperature in Damage
Physics - push deeper into the mechanisms more
data TCAD, etc.
Continue to Push More Deeply into New Types of
SiGe Devices - SiGe MODFET SiGe HBT on SOI
complementary SiGe (npn vs pnp)
Publications 1 A.K. Sutton, A.P.G. Prakash,
R.M. Diestelhorst, G. Espinel, B. Jun, M. Carts,
A. Phan, J.D. Cressler, P.W. Marshall, C.J.
Marshall, R.A. Reed, R.D. Schrimpf, and D.M.
Fleetwood, An Investigation of Dose
Enhancement and Source Dependent Effects in
200 GHz SiGe HBTs, IEEE Nuclear and Space
Radiation Effects Conference, July 2006.
2 G. Prakash, R. Diestelhorst, G. Espinel,
A. Sutton, B. Jun, C. Marshall, P. Marshall, and
J.D. Cressler, The Effects of 63 MeV Proton
Irradiation on SiGe HBTs Operating at Liquid
Nitrogen Temperature, Proceedings of the
Seventh IEEE European Workshop on Low-Temperature
Electronics, June 2006. 3 M. Bellini, B. Jun,
T. Chen, J.D. Cressler, P.W. Marshall, D. Chen,
and J. Cai, Radiation and Bias Effects in
Fully-Depleted and Partially-Depleted SiGe HBTs
Fabricated on CMOS-Compatible SOI, 2006 IEEE
Nuclear and Space Radiation Effects
Conference, July 2006. 4 A.P.G. Prakash, A.K.
Sutton, R. Diestelhorst, G. Espinel, J. Andrews,
B. Jun, J.D. Cressler, P.W. Marshall, and C.J.
Marshall, The Effects of Irradiation Temperature
on the Proton Response of SiGe HBTs, 2006 IEEE
Nuclear and Space Radiation Effects Conference,
July 2006.